This invention relates to noise simulators and, in particular, to injection of simulated-noise signals in the power line of electrical equipment under test and to generators for generating simulating-noise signals, such as a square wave for lightening strike simulation and a damped wave for ringing surge simulation.
Certain electrical or electronic equipment such as data processors and the like are sensitive to power-line noise such as voltage dips and high-frequency transients conducted through the power line, and are subject to malfunction due to the power-line noise. In order to evaluate the sensitivity of equipment to power-line noise, noise simulators are used which artificially produce power-line noise to supply the same to equipment under test through their power lines.
Such a noise simulator is disclosed in "Noise Simulators Help Find Peril in Power-line Defects" described by Mr. M. L. Tandon in Electronics, Mar. 7, 1966, pp. 117-121. In the noise simulator disclosed therein, power-line disturbances such as voltage dips and high-frequency transient noises are generated for evaluation of electrical equipment with such noise.
Thereafter, it has been noted that low-frequency surge noises such as lightening strikes and ringing surges also plague sensitive equipment such as data processors. Lightening strikes or surge noises are conducted to equipment through the power line and may defeat or erroneously operate the equipment.
Ringing surges are low-frequency damped-wave noises due to turn-on or -off of AC power to other electrical devices having inductance or capacitance such as electric motors, transformers, phase-advance condensers and the like.
For simulation of lightening strikes and ringing surges, noise simulators are desired to generate simulated lightening strikes and simulated ringing surges.
In noise simulators, a filter having an inductance coil and a capacitor is used in the power line of the equipment under test. AC power current always flows through the inductance coil to cause a voltage drop. In certain cases, a transformer is used in place of the inductance coil to inject simulated-noise signals therethrough. However, the use of a transformer is not desired for the injection of high-energy signals because a large transformer must be used.